Combined electromagnetic and thermal protective circuit breaker system



Jan. 6, 1948.- H, M. WILSON GOBINED ELECTROMAGNETIC AND THERMAL PROTECTIVE CIRCUIT BREAKER SYSTEI Filed April 22, 1943 2 Sheets-Sheet 1 FIG-l. 3/

Jan. 6, 1948. H. M. WILSON COMBINED ELECTROMAGNETIC AND THERMAL PROTECTIVE CIRCUIT BREAKER S YSTEM Filed April 22, 1943 2 Sheets-Sheet 2 Patented Jan. 6, 1948 COMBINED ELECTROMAGNETIC AND THEE- MAL PROTECTIVE CIRCUIT BREAKER SYSTEM Harold M. Wilson, Arlington,

Metals Mass,

& Controls Corporation, a corporation of Massachusetts Mass, assignor to Attleboro,

Application April 22, 1943, Serial No. 483,984

' 3 Claims. (01. its-e94) This invention relates to circuit breakers, and

with regard to certain more specific features, to remote-control circuit breakers for use on aircraft and the like. Among the several objects of the invention may be noted the provision of a simple form of manual reset, trip-free, combination magnetic and thermal circuit breaker to protect a circuit from overheating, by opening the circuit if currents of dangerous value flow therein; theprovision of certain forms of apparatus of the class described arranged to permit placement of a switch on an operating panel without the use of large copper conductors to outlying devices; and the provision of apparatus of the class described which permits the use of a remote-controlled circuit breaker as larg as needed near an outlying device. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which are illustrated several of various possible embodiments of the invention,

Fig. 1 is a vertical section and wire diagram showing one form of my invention; and,

Figs. 2, 3 and 4 are similar views, respectively showing modifications.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Referring now more particularly to Fig. 1, there is shown at numeral l a load consisting of a motor or similar translating device in a load circuit 3. This draws current in said circuit 3. Circuit 3 includes a solenoid coil 5, fixed in a case I and surrounding a guide 9. Sliding in the guid 9 is a magnetic armature core II which has an outside head l3. This core is normally biased from the solenoid by a spring l5, which reacts against the head 13. The spring l5 reacts from a flanged portion 2 of the guide 9, this flanged portion also acting as a stop limiting the outward movement of the core H.

The head i3 passesthrough an opening a composite thermostatic conducting member l9. Preferably this should be of the snap-acting disc type generally known in the art as a Spencer disc. This disc is cupped and carries contacts 2| engageable with contacts 23, the latter being supported upon, but insulated from, the case I.

The contacts 23 are in a battery feed circuit 25 which, when the contacts 2| and 23 are closed, places the disc 19, which is conducting, in series with the load I and a supply battery 21. also closes a holding circuit through the coil 5, as will appear. The disc I9 is non-rotary, this being accomplished by a fixed pin I0 passing through an opening l2 in the disc, or other suitable means to accomplish this end may be used. This maintains alignment between contacts 2| and 23. It is to be understood however that the disc is loosely mounted on H between th flanges shown to permit free flexing.

At 29 is shown a threaded adjustable stop adapted to be locked in any adjusted position by means of a lock nut 3|. This stop 29 is engageable by the armature II when the same is drawn inward by action of the solenoid coil 5. When this action occurs, the spring 15 is compressed.

A handle 33 is carried on the head l3 for manual push-pull manipulation. Operation is as follows:

The spring l5 normally biases the armature l I along with th thermostatic disc IS in contactopening direction to the open circuit position shown. This that the battery 21 does not feed the load I. By temporarily manually pushing in on the button 33, that is, by manually resetting the switch so that the contacts 2| and 23 close, a circuit is closed including the load I and the battery 21, and at the same time a holding circuit is closed through th solenoid 5 which immediately engenders a flux field operating on the armature H. This takes charge in biasing the disc [9 in contact-closing direction so as to hold shut the contacts 2| and 23. Then, even though the operator releases the button 33, the battery circuit 25 remains closed through the load I. The operator may, however, open the-circuit at will by pulling the knob 33.

Next, assuming the circuit to be closed, it an overload occurs from the load I, more current passes through. the conducting disc l9, which upon heating above a' substantially predetermined temperature snaps from the curvature shown to an opposite curvature (concave downwardly instead of upwardly) which opens the circuit so as to drop the load from the battery 21 and to deenergize the solenoid 5. It will be understood that the stop 29 is set so that after the disc I! snaps to open circuit position, and

while it is still hot, it cannot be pushed into closed circuit position. Also if manually initiated reclosure is attempted under overload conditions.

This

breaks the battery circuit 25 so even with th disc snapped back to its'cold curvature, the device will open. That is to say, the device is trip-tree, opening when required under overload conditions being free or manually initiated holding actions.

As soon as the so enoid is deenergized, the spring I5 forces the armature II to the solidline position shown, in which, when the disc is again cools, there will be no reclosing oi .the contacts 2| and 23 until manual pushing operation is again performed upon the button 33.

In Fig. 2 is shown a, modification in which like numerals designate like parts. The circuit in .this case diners from that at Fig. 1 as follows:

A remote-control push-button switch 30 having closing contacts 32 is used for connecting contacts 35. A spring 31 normally biases open the switch 30. Thus the button 35 becomes a remotecontrol momentary reset device. When the contacts 32, 35 are temporarily closed, a circuit is closed from the battery over power lines 38, 39, solenoid 5, and line 4|, back to the battery 21. This energizes the solenoid 5 to draw in the armature core Ii, so as to close the contacts 2|, 23, provided the thermostatic disc |9 is in its cold position shown in Fig. 2, As soon as the contacts 2 23 are closed, the battery circuit is closed over line 43 through the load. Since the disc I! carries current, a line 45 connected therewith by means of a pigtail 41 becomes energized to maintain the circuit through the solenoid 5. Therefore, the button 30 may be released without impairing the holding characteristics of the solenoid 5. The core II is held in against the normal expansive action of the spring i5. These conditions continue until an overload occurs in the load whereupon the current in the disc I! overheats it, so that it snaps to its opposite curvature, thus breaking the contacts 2 23. This immediately opens the load circuit and also the solenoid circuit'5, so that the spring l5 pushes the disc isaway from the contact 23.. Hence, even if the disc snaps to its cold position, the circuit will not automatically reclose. However, it can be reclosed by pushing in the momentary contacts 30 whenever desired. This device, like the one shown in Fig. 1, is trip-free, because if an attempt is made to reclose before the disc l9 has snapped toits cold position, nothing will occur except that the armature I I- will be drawn against the stop 29 without closing the contacts 2|, '23. Also, the switch will persist in reopening even though under overload conditions manually initiated reclosure is attempted after the disc has snapped back to its cold curvature.

In Fig. 3 is shown a third form of the invention, in which like numerals designate like parts. In this case, the starter button 30 is organized with the solenoid 5 as in Fig. 2, and the load is organized with the battery 21, disc is, contacts 2| and 23, as before, through circuit 43. In this case, however, the device is equipped with a remote-control stop button switch consisting of contacts 49 in the line 45 of the holding circuit and contacts 5|, which are under control of a stop button 53. Circuit 45 is closed through the pigtail connection 41 with the disc IS. The contact 5| and the button 53 are biased toward closed circuit position by a spring 55. The operation of this form of the invention is like that of Fig. 2, except that the circuit may be remotely manually opened at will after having once been closed by pushing the momentary stop button which the snap-acting thermostatic disc is not called upon to carry all or the load current, but

is arranged in shunt. In this figure, like numerals again designate like parts.

i In thisiorm oi the invention, the contacts 2|, instead of being carried upon the snap-acting disc ii, are carried upon a bus bar 51- which is riveted to the armature core II as indicated at 5!.

Threaded into the end of the core II is an insulating pin' II. A screw 53 holds the central portion of the snap-acting disc I! on this insulating pin or plugll.

An extra set of contacts 55 is carried on the bus bar 51, and these are engaged and disengaged by contacts 51 carried upon the thermostatic, snap-acting disc [3.

As in Fig. 2, a remote reset momentary contact switch is shown with appurtenant parts, numbered as in Fig. 2. When momentarily pressed, this switch closes-the circuit 35, 33, 4| through the battery 21 and the solenoid 5 to pull up the armature core II. This closes the contacts 2|,

- 23 and thus by means of the bus bar 5i closes the load circuit. This circuit includes the battery 21, contacts 2|, 23, the bar 51, line 43' and the load- I. Since the disc i5 is at this time presumed to be cold, contacts 65, 51 are closed as shown, which places the disc 19 in shunt circuit'with the bus bar 51. Thus current flows over the line 45 and back to the battery 21 via solenoid 5 and wire 4|. v

The disc I! is calibrated to heat and snap to open circuit position at predetermined overload shunt current across the bar 51. Since the disc I9 controls a holding circuit through the solenoid 5, snapping open oi the disc under overload conditions results in release of the armature core H and outward movement of the bar 51 under bias of spring l5. This reopens the contacts 2|, 23, thus breaking the load circuit from the battery 21.

In this Fig. 4 form of the invention, there is no need for any stop for the core because the contacts 2|, 23 form a stop, being all rigidly mounted. Also, the fixed alignment pin l4 passes through openings l5 and il in 51 and I5 respectively. This form of the invention is not tripfree, because even when the disc I! is in hot, open position (downwardly convex) a holding circuit may be temporarily closed through the solenoid 5 by pressing button 3|. However, as soon as the button is released, this holding circuit is reopened, and the circuit opened, since then there is no holding circuit through the disc l8.

It should be understood that the thermostatic member is, while preferably composed of a snapacting disc of the Spencer type may, under circumstances of low current value in the work circuit, be of a strip, creep-acting or other type.

It will be recognized that the coil 5 need not draw the same amount oi current as the load circuit, in fact, much less. Thus, if desired, the wiring to the momentary contact switches may be made relatively small. Hence, the constructions of Figs. 2, 3 and 4 may employ momentary contact switches on an instrument panel near a pilot with as extensive an amount of the lighter wire as is needed. The solenoid-controlled thermostaticswitch may then be placed adjacent to the motor or other load without involving a large amount of heavy wire.

From Fig. 1 it will be seen that one way of initially energizing the holding circuit through the coil 5 is to push the assembly of the arma ture and thermostatic member (when cold) into circuit closing position. This principle may be applied to the constructions shown in Figs. 2, 3 and 4 if it is desired to eliminate the auxiliary push-button-control holding circuits. ,In general, the latter are desirable, since they permit the use of the small wires carrying only a small amount of current from the thermostatic switch to the control board. It is desirable to save heavy wires, particularly where there are as many oi them as in an airplane. At the same time, it allows the thermostatic member I9 to be located close to the translating load member if it be desired to protectthis device against overheating. bly or solenoid coil, solenoid armature and thermostatic member may be strapped directly to a motor or generator and the wires tothe push button switch such as shown at 39 in Fig. 2 carried over to the pilot's instrument panel. The same is true or the structures shown in Figs. 3 and 4, wherein it is clear that the momentary contact make-or-break switch need not carry heavy-current for operating the solenoid coil. It is to be understood however that said assembly need not be near the device I where the object is simply protection against overload currents. As above stated, one o! the characteristics 01 the solenoid coil is that it may be designed for light current values.

In view of the above, it will be seen that the several objects of the invention'are achieved and other advantageous results attained.

accuse For example, in such instances, the assem- As many changes could be made in the above constructions without departing from the scope or the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A manually resettable trip-tree circuit breaker for automatically breaking a load circuit upon overload. comprising a thermostatic switch adapted to make and break a load circuit, said switch comprising separable contacts, an electrically conductive thermostatic member controlling said contacts and included in the load circuit when the contacts are closed, said thermostatic member being adapted to open said contacts upon heating above a substantially predetermined temperature due to passage of overload current therethrough, means biasinz said thermostatic member in a contact-opening direction, a solenoid which, when energized, biases 6. said member in a contact-closing direction, a holding circuit including said solenoid and thermostatic switch whereby said solenoid is energized when said contacts are closed, manually operable means for moving said thermostatic member in contact-closing direction, and means for limiting movement of said member in contact-closing direction to prevent closing of the contacts when said member is heated above said temperature.

2. A manually resettable trip-free circuit breaker for automatically breaking a load circuit upon overload, comprising a thermostatic switch adapted to make and break a load circuit,

said switch comprising separable contacts, an electrically conductive thermostatic member controlling said contacts and included in the load circuit when the contacts are closed, said thermostatic member being adapted to open said contacts upon heating above a substantially-predetermined temperature dueto passage of overload current therethrough, means biasing said thermostatic member in contact-opening direction, a solenoid which, when energized, biases said member in contact-closing direction, a holding circuit including said solenoid and thermostatic switch whereby said solenoid is energized when said contacts are closed,'said solenoid being connected in a power circuit'including a normally open manually operable switch, whereby said thermostatic member may be moved in a contactclosing direction by said solenoid by closing said manually operable switch, and means for limiting movement of said member in a contact-closing direction to prevent closing or the contacts when said member is heated above said. temperature. w

3. A circuit breaker as set forth in claim 2, further including a normally closed manually operable switch in said holding circ'uit whereby said solenoid may be deenergized to permit the biasing means to bias said thermostatic member to open the contacts.

HAROLD M. WILSON.

REFERENCES CITED The following references are of record in the tile oi. this patent:

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